Sch 10 para 31
An appeal against a determination of a devolution issue by— (a) a court of two or more judges of the High Court of Justiciary (whether in the ordinary course of proceedings or on a reference under paragraph 27); or (b) a court of three or more judges of the Court of Session from which there is no appeal to the Supreme Court apart from this paragraph , shall lie to the Supreme Court , but only with permission of the court concerned or, failing such permission , with permission of the Supreme Court .